How did the US end up having 538 electoral college members?

Answer 1

There is one for each U.S. Senator, one for each U.S. Representative, and three for D.C. Each state is allowed to appoint a number of electors equal to the total number of U.S. Senators and U.S. Representatives to which the state will be entitled on the next Inauguration Day.

Each state is entitled to two U.S. Senators, so as long as there are 50 states there will be 100 Senators (not counting occasional vacancies).

After every U.S. census, the U.S. Census Bureau recalculates how many congressional districts each state will have. Each congressional district elects one Representative, so the number of congressional districts equals the total number of voting members of the House. After a minimum of one, each state's share of Representatives needs to be proportional to its share of the U.S. population. Congress is free to choose the total number of Representatives as long as no congressional district ends up with less than 30,000 residents. In 1929, Congress voted to freeze the total number of Representatives at 435, the number it went up to when Arizona became a state over 100 years ago. Despite numerous warnings from several of the founding fathers regarding the importance of setting a maximum district size in the Constitution, such a proposal has yet to be ratified. Their recommendations for the maximum district size ranged from 30,000 residents to 60,000 residents (none of them thought a congressional district should ever have more than 60,000 residents). The average congressional district size today is over 710,000 residents, and when the Montana population topped 1,000,000 earlier this decade was the first time we had a single congressional district with over a million residents. (For more information on this topic, visit www dot thirty-thousand dot org.)

The 23rd Amendment to the U.S. Constitution, ratified on March 29, 1961, allows the District of Columbia to appoint the number of electors they would appoint if they were a state (currently 3) or the number of electors appointed by the least populous state (also currently 3), whichever is lower.

100 + 435 + 3 = 538